IDEs

Padre is a cross-platform, open-source, free, IDE for Perl, written in Perl,
and which is under active development. It's probably the most recommended for
most people who don't have a previous preference.

Komodo Edit is a cross-platform, costless, open-source, editor for Perl, and
other dynamic languages by ActiveState. Komodo IDE is a commercially-enhanced
version of it which is not open-source and costs money.

Vim is a popular open-source, cross-platform, and free editor, with good
support for editing Perl code.
the
Perl 5 Wiki page about Vim contains more information.

By default Vim behaves very much like the ubiquitous UNIX editor
vi, which may seem foreign
to people used to the conventions of modern desktop environments. However,
using
mswin.vim it can behave much more like Windows-based editors.

TextMate is a commercial (but now open source under the GPL version 3)
programmers' text editor that has become popular on Mac OS X, and E Text
Editor is a commercial version of it for Windows, with source available for
compiling on Linux and other systems.

Other Lists

These are other lists of prominent or notable IDEs - not all of them are
Perl-oriented.

Helper Tools

perltidy is an auto-formatter for Perl code, that can keep its style
consistent. It supports many different styles and style parameters. Perltidy
has a frontend
called tidyview that allows one to visually customise the style and
view the results.

Graphical Debugger Front-ends

While not full-fledged IDEs, these tools are useful as graphical debugger
front-ends.

Devel-ptkdb - a Perl/Tk based graphical debugger. Was
not maintained since 2004, but may still get the job done.